Dr. Philip Dowd Profile

Dr. Philip Dowd

SPIE Involvement:

Author

Proceedings Article | 24 August 2005 Paper

Two-color infrared focal plane array based on InAs/InGaAs/GaAs quantum dots in a well detectors design

Senthil Annamalai, Philip Dowd, Darren Forman, Petros Varangis, Tom Tumolillo, Allen Gray, Kathy Sun, Mingguo Liu, Joe Campbell, Daniel Carothers, Sanjay Krishna

Proceedings Volume 5897, 58970P (2005) https://doi.org/10.1117/12.617775

KEYWORDS: Staring arrays, Sensors, Long wavelength infrared, Quantum dots, Thermography, Infrared radiation, Gallium arsenide, Mid-IR, Infrared sensors, Quantum well infrared photodetectors

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Proceedings Article | 29 December 2004 Paper

Quantum dot detectors for mid-infrared sensing: bias-controlled spectral tuning and matched filtering

Unal Sakoglu, Zhipeng Wang, Majeed Hayat, J. Scott Tyo, Senthil Annamalai, Philip Dowd, Sanjay Krishna

Proceedings Volume 5593, (2004) https://doi.org/10.1117/12.571326

KEYWORDS: Sensors, Optical filters, Reconstruction algorithms, Signal to noise ratio, Detection and tracking algorithms, Quantum dots, Image filtering, FT-IR spectroscopy, Spectroscopy, Black bodies

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Quantum-dot infrared photodetectors (QDIPs), based on intersubband transitions in nanoscale self-assembled dots, are perceived as a promising technology for mid-infrared-regime sensing since they are based on a mature GaAs technology, are sensitive to normal incidence radiation, exhibit large quantum confined stark effect that can be exploited for hyperspectral imaging, and have lower dark currents than their quantum well counterparts. High detectivity (D* = 1.0E11 cmHz^1/2/W at 9 microns) QDIPs have been recently shown to exhibit broad spectral responses approximately 2-micron FWHM) with a bias-dependent shift in their peak wavelengths. This controllable, bias dependent spectral diversity, in conjunction with signal-processing strategies, allows us to extend the operation of the QDIP sensors to a new modality that enables us to achieve: (1) spectral tunability (single- or multi-color) in the range 2-12 microns in the presence of the QDIP's dark current; and (2) multispectral matched filtering in the same range. The spectral tuning is achieved by forming an optimal weighted sum of multiple photocurrent measurements, taken of the object to be probed, one for each bias in a set of prescribed operational biases. For each desired spectral response, the number and values of the prescribed biases and their associated weights are tailored so that the superposition response is as close as possible, in the mean-square-error sense, to the response of a sensor that is optically tuned to the desired spectrum. The spectral matching is achieved similarly but with a different criterion for selecting the weights and biases. They are selected, in conjunction with orthogonal-subspace-projection principles in hyperspectral classification, to nullify the interfering spectral signatures and maximize the signal-to noise ratio of the output. This, in turn, optimizes the classification of the objects according to their spectral signatures. Experimental results will be presented to demonstrate the QDIP sensor's capabilities in these new modalities. The effect of dark current noise on the spectral-tuning capability is particularly investigated. Examples of narrowband and wideband multispectral photocurrent synthesis as well as matched filtering are presented.

Proceedings Article | 15 October 2004 Paper

Real-time implementation of matched filtering algorithms using adaptive focal-plane array technology

Zhipeng Wang, Unal Sakoglu, Senthil Annamalai, Nina-Rae Weisse-Bernstein, Philip Dowd, J. Scott Tyo, Majeed Hayat, Sanjay Krishna

Proceedings Volume 5546, (2004) https://doi.org/10.1117/12.560116

KEYWORDS: Sensors, Space sensors, Signal to noise ratio, Staring arrays, Infrared radiation, Photodetectors, Quantum well infrared photodetectors, Infrared photography, Image processing, Spectral resolution

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Proceedings Article | 8 December 2003 Paper

1.3-µm GaAsSb/GaAs VCSELs

Philip Dowd, Shane Johnson, Sergio Chaparro, Stewart Feld, Matthew Horning, Martin Adamcyk, Yong-Hang Zhang

Proceedings Volume 5248, (2003) https://doi.org/10.1117/12.512732

KEYWORDS: Vertical cavity surface emitting lasers, Semiconducting wafers, Reliability, Continuous wave operation, Gallium arsenide, Quantum wells, Doping, Wafer-level optics, Reflectivity

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SPIE Journal Paper | 1 September 2002

Analysis and modeling of distributed feedback and distributed Bragg reflector lasers using regrowth-free index-coupled surface grating technology

Hery Susanto Djie, Chrisada Sookdhis, Philip Dowd

OE, Vol. 41, Issue 09, (September 2002) https://doi.org/10.1117/12.10.1117/1.1496114

KEYWORDS: Seaborgium, Etching, Refractive index, Laser applications, Optical simulations, Distributed Bragg reflectors, Quantum wells, Semiconductor lasers, Optical engineering, Waveguides

Proceedings Article | 29 October 2001 Paper

Analysis and structure design of distributed-feedback laser (DFB) and distributed Bragg reflector (DBR) laser using regrowth-free surface grating technology

Hery Susanto Djie, Chrisada Sookdhis, Philip Dowd

Proceedings Volume 4594, (2001) https://doi.org/10.1117/12.446552

KEYWORDS: Etching, Waveguides, Refractive index, Optical design, Laser applications, Structural design, Distributed Bragg reflectors, Laser development, Quantum wells, GRIN lenses

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Proceedings Article | 28 September 2001 Paper

Method to achieve large displacements using comb drive actuators

Guangya Zhou, Duongsin Low, Philip Dowd

Proceedings Volume 4557, (2001) https://doi.org/10.1117/12.442975

KEYWORDS: Actuators, Micromachining, Electromechanical design, Standards development, Surface micromachining

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Proceedings Article | 16 April 2001 Paper

Diffractive optical elements designed by hybrid genetic algorithm for the generation of nondiffracting beams

Guangya Zhou, XiaoCong Yuan, Philip Dowd, Yee Loy Lam, Yuen Chuen Chan

Proceedings Volume 4291, (2001) https://doi.org/10.1117/12.424849

KEYWORDS: Optical design, Diffractive optical elements, Genetic algorithms, Nondiffracting beams, Holography, Integrated photonics, System integration

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Proceedings Article | 27 April 2000 Paper

Integration of 32x32 photodiode arrays with silicon for massively parallel optical interconnects

Chang Ryu, Bernhard Koelle, Shane Johnson, Philip Dowd, Raenaurd Turpin, S. Adhiveeraraghavan, Jin Xu, YongHang Zhang, Daniel Docter

Proceedings Volume 3952, (2000) https://doi.org/10.1117/12.384389

KEYWORDS: Photodiodes, Silicon, Metals, Optical interconnects, PIN photodiodes, Vertical cavity surface emitting lasers, Gold, Indium, Aluminum, Absorption

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Proceedings Article | 30 April 1999 Paper

Optical interconnects for high-speed data links

Chang Ryu, Bernhard Koelle, Shane Johnson, Philip Dowd, Raenaurd Turpin, Parag Kelkar, YongHang Zhang

Proceedings Volume 3631, (1999) https://doi.org/10.1117/12.348313

KEYWORDS: Vertical cavity surface emitting lasers, Silicon, Modulation, Gallium arsenide, Glasses, Indium, Optical interconnects, Mirrors, Eye, Indium gallium arsenide

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Showing 5 of 10 publications

Conference Committee Involvement (1)

International Symposium on Photonics and Applications

26 November 2001 | Singapore, Singapore

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